It is well known that stepped hulls and multiple stepped hulls can be used on water borne apparatus to reduce the area of engagement between the hull and the water, thereby reducing the drag caused by the water and increasing the efficiency of the apparatus. Under present designs, this is accomplished by building the inclined plane of each step so that the angle of attack between the step surface and the water surface forces the hull upwards and reduces the wetted area of the hull. This conventional stepped hull, however, has only one speed at which the efficiency of the hull is at its optimum. The greater the distance between the steps, the higher the optimum speed of the hull, and the closer the steps are together, the slower the optimum speed. These hulls are designed such that the lower points or lower termination edges (or termini) of all the steps are substantially on a straight line if viewed in a longitudinal profile parallel to and adjacent to the keel. With this configuration, all steps are in contact with the water at every speed.
As the steps move through the water, they depress the immediately surrounding water thereby creating waves which move at constant speed through the water. As the speed of the apparatus increases, the waves have less time to rebound between the steps, so that in prior designs, the rear of the boat will drop until the latter steps are depressed enough into the water to engage a sufficient amount of water to support the stern of the boat. This causes the steps to plow a progressively deeper trough in the water which increases drag and gives the boat an undesirable raised bow attitude.
Accordingly, the principal objects of the present invention are to provide a flotation apparatus which minimizes the deficiencies in the present designs by providing means to maintain the apparatus substantially level as it moves through the water, while at the same time allowing predetermined numbers of individual steps to rise above the surface of the water as the speed of the apparatus increases, thereby reducing the drag caused by the water and increasing the efficiency of movement.
Another object of the invention is to provide a range of optimum speeds by progressively reducing the surface area in contact with the water as the speed of the apparatus increases, and to maintain the apparatus in an essentially horizontal orientation, rather than allowing it to assume an undesirably high bow attitude.
Additionally, the present invention provides for more than one optimum speed depending upon the numbers of steps chosen, and their orientation relative to one another.